1. Field of the Invention
This invention relates to a display device, a display method and a head-up display.
2. Background Art
There is a head-up display HUD (Head-Up Display) allowing driving information such as vehicle speed and traveling direction indication or the like projected on a windscreen to be viewed and external information and travel information to be visually identified simultaneously.
In a normal HUD a display image is observed by both eyes, however a single eyed HUD which the display image is visually identified by a one-eye is proposed for improving visual identification. For example, JP-A 7-228172 (Kokai)(1995) discloses a technique concerning a single eyed HUD presenting the display image to only one eye of an observer for the sake of preventing double images in visual identification with both eyes. A technique presenting the display image to only one-eye is also investigated for enhancing a sense of depth. Furthermore, in the HUD, whereas display brightness is low relative to bright environment in day time, a probable idea is a display with limiting a display region to a part of eyes, particularly one-eye, to improve the brightness and increasing a life time of a light source.
Thus, in a display device with the display region narrowed, alignment of the display region and the eye is important particularly in the case of visual identification by the one-eye.
Here, in control of position of the display region, it is important to select which eye of right and left eyes as the eye of a mark for the alignment.
That is, it is generally said that a human has a dominant eye (ascendant eye). When the image is visually identified with a one-eye, the visual identification with a one-eye other than the dominant eye may cause a visual rivalry to make the visual identification of the image difficult, however the visual identification with the dominant eye generate little visual rivalry to allow the natural visual identification of the image. Therefore, in a single eyed display device, it is desirable to display the image on the dominant eye. That is, it is desirable to use the dominant eye as a mark of the position of the display region.
One example of detection method of the dominant eye is as follows. For example, first, something to be a mark (what can be seen two or three meters ahead) is indicated with a forefinger, at this time an arm is stretched straight without tilting a face and the forefinger is placed in front of the face. While opening both eyes, focusing on the mark is obtained and the eyes are closed with the pose as it is. Here, an eye presenting the image with smaller displacement from the image with both eyes is the dominant eye. Another example of detection method of the dominant eye is as follows. For example, a suitable mark is seen by both eyes while holding a sheet of paper with a hole of a diameter of 1 to 2 cm with both hands upright. While seeing the mark, the sheet of paper is brought near short (toward the face). When the paper is brought near to the front of the eyes, an eye with which a hole is peeped through turns to be the dominant hole.
Conventionally, there has been no automatic detection method of the dominant eye, thus when the image is projected on the dominant eye in the single eyed display device, it is necessary that the identifier himself sets an eye serving as a mark for control of the position of the display region and it has been inconvenient.
It is noted that JP 3279913 discloses a technique concerning personal identification for specifying location of the identifier.